1. Field of the Invention
The invention relates to cooling devices for computers, and in particular to cooling fans configured to remove heat generated by components within a personal computer.
2. Background of the Invention
Computers are widely used in our lives. Development of materials science and electronics technologies has boosted the speed and lowered the dimensions of microprocessors in recent years. This has enabled computer manufacturers to develop and launch more powerful computers having smaller sizes. However, computer components cased in a chassis—motherboards in particular—generate more heat as they operate at higher speeds. This additional heat generated must be removed from the chassis with cooling fans or other cooling means.
A traditional cooling fan or fan assembly for a personal computer is shown in FIG. 1. In this traditional cooling fan, fan blades 10 inside the outer frame 20 are driven by an output shaft of a motor to generate a flow of air. To create ventilation to allow the exchange of heat with the airflow, openings are formed in the frame 20 to create air channels 30 through the fan assembly. The center of the frame 20 includes a block 40, here having a circular shape, which is approximately centered on the axis of rotation of the fan. When the blades 10 rotate during operation of the fan, air is forced through the air channels 30, which lie on the same plane as the inner face of the frame 20. This fan assembly is then attached to a chassis of a computer, where the chassis includes a number of air channels to allow a flow of air through the chassis and fan.
Although the fan of FIG. 1 can offer a basic cooling functionality, this fan generates a near elliptic disturbed flow zone 50 in front of the near circular block 40 due to the blocking of the airflow by the block 40, as shown in FIG. 3. Moreover, the distance between the block 40 and the output shaft 60 of the motor (or blade trunnion) is about the same as that between the frame 20 and the output shaft 60, which can cause blade vibration and hence an undesirable noise.